Use random.uniform(a, b):
>>> random.uniform(1.5, 1.9)1.8733202628557872
if you want generate a random float with N digits to the right of point, you can make this :
the second argument is the number of decimals.
random.uniform(a, b) appears to be what your looking for. From the docs:
Return a random floating point number N such that a <= N <= b for a <= b and b <= N <= a for b < a.